Faulty MCAS system was poorly developed, rushed through testing, and concealed from pilots.

Boeing CEO Dennis Muilenburg testified at two U.S. Congressional hearings on the 737 MAX disasters—and his testimony raised more questions than answers.

“Mr. Muilenburg’s answers to our questions were consistent with a culture of concealment and opaqueness and reflected the immense pressure exerted on Boeing employees during the development and production of the 737 Max,” said Representative Peter DeFazio, chairman of the House Transportation & Infrastructure Committee, and Representative Rick Larsen, leader of its aviation sub-panel, in a letter following the hearings.

Why Weren’t Pilots Trained on the MCAS?

One of the key subjects to come out of the hearings was on whether pilots were properly prepared and trained to handle emergencies like the ones that caused the two plane crashes.

In both accidents, the Maneuvering Characteristics Augmentation System (MCAS) erroneously activated and repeatedly pitched the nose of the aircraft down despite the struggles of the pilots to keep the plane level.

The pilots didn’t even know about the MCAS because Boeing had reference to the system removed from the pilots’ training manual. The planemaker told the FAA that the MCAS was a benign background system that didn't need to be included in training and flight deck manuals.

In addition, a cockpit indicator that would have notified pilots of a MCAS malfunction was designed, but it was never installed in the final version of the aircraft. And an AOA Disagree alert, which would have lit up if the angle-of-attack sensor malfunctioned, was inoperative on most MAX jets.

Muilenburg has claimed in the past that pilots needed to be trained on the MCAS, that it was fundamentally embedded in the flight controls of the plane—essentially, pilots were trained on the MCAS when they were trained on the aircraft.

One of Boeing’s assumptions in developing the MCAS was that, if it activated erroneously, pilots would be able to recognize it within four seconds and would know how to shut it off. According to Boeing documents obtained by Congress, “A slow reaction time scenario, 10 seconds, found the failure to be catastrophic.”

A recent U.S. National Transportation Safety Board (NTSB) report found Boeing was wrong in its assumptions, underestimating how long it would take pilots to respond to the MCAS’ failure—particularly since they would have to deal with multiple blaring alerts, flashing lights and a shaking control stick while the plane veered out of control.

The report also stated that Boeing’s own MCAS simulator tests didn’t factor in the failure of an angle-of-attack sensor, which would have triggered other alerts and warnings that wouldn’t activate in other situations, further slowing the pilots’ reaction times.

“I've talked to a lot of pissed off pilots,” said Transportation Committee Chair Peter DeFazio, D-Oregon, to Muilenburg at the hearing. “They said, 'We were the backup system? How can we be backup if we don't know something's going to take over our plane?'”

The hearings also revealed that Boeing made considerable efforts to minimize pilot training for the MAX—which influenced the decision to not include the MCAS in the training requirements. This included costly and lengthy time in the simulator. In fact, Boeing offered Southwest Airlines a $1-million discount per plane if pilots needed simulator training to operate the jet.

What Did Boeing Know, and When?

Internal documents given to Congress show that there were worries inside Boeing about the MCAS and its over-reliance on one angle-of-attack sensor even as the plane was being rolled out.

In one email, sent in 2015—a year before the MAX was certified—a Boeing employee asked if the MCAS was vulnerable to a malfunction if the single AOA sensor failed, writing, “Are we vulnerable to single AOA sensor failures with the MCAS implementation or is there some checking that occurs?”

In internal text messages from 2016, Boeing’s test pilot, Mark Forkner, said he had difficulties with the MCAS in simulator tests—saying at one point, “it’s running rampant in the sim on me.” Forkner would later downplay the system’s risk to the FAA: “so basically, I lied to the regulators unknowingly.”

In one heated exchange at the hearings, Muilenburg admitted knowing after the first crash and before the second about internal messages from 2016 between pilots that discussed “egregious” problems in the MCAS. Boeing’s CEO said he didn’t read them fully at the time and forwarded them to Boeing’s legal department. This drew an angry response from senator Ted Cruz: “You're the CEO, the buck stops with you. How did your team not put in front of you, run in with their hair on fire saying, ‘We've got a real problem here’?”

Boeing CEO gets grilled by Congress.

Boeing has created a fund for the victims, is fixing the MCAS and has committed to continuing to learn from its mistakes. And while the 737 MAX is inching closer to re-certification, the fallout from the two crashed aircraft will still hang over the company for a long time.

“Our investigation has already shown that Boeing leadership was aware of many of the problems that engineers are now attempting to fix during the design and development phase of the 737 MAX,” said DeFazio and Larsen in their letter. “The bottom line is that there are a lot of unanswered questions, and our investigation has a long way to go to get the answers everyone deserves.”